The invention relates to a solenoid valve having a clapper armature, yoke and yoke pins coupled to the clapper armature, which is capable of high reliability and small size.
Solenoid valves are used for control systems of all types and generally comprise a valve housing, an electromagnet, which has a coil, a yoke and an armature, and at least one valve seat and a sealing element which can be actuated by the armature and which co-operates with the valve seat. A particular distinction is drawn between the principle of plunger-type armatures and clapper-type armatures in the configuration of the electromagnet, in particular with regard to the armature.
In order to be able to ensure reliable operation of magnetic valves with power consumption which is as low as possible, fine tolerances must be complied with or compensated for when the individual elements are manufactured and when the solenoid valve is assembled.
There is the additional desire in the field of pneumatics to have smaller and smaller valves. The result in small solenoid valves, even with very fine tolerances, is that a reliable function cannot always be ensured with low power levels and small stroke actions owing to the sum of the individual tolerances.
Therefore, the problem addressed by the invention is further to develop the solenoid valve so that a reliable function can likewise be ensured with small solenoid valves.
The solenoid valve according to the invention substantially comprises the following components: a valve housing, an electromagnet having a coil, a yoke and a clapper armature, at least a first valve seat and a sealing element which can be actuated by the clapper armature and which co-operates with the first valve seat. The yoke has yoke pins and the armature is arranged on a yoke pin at the end thereof that is remote from the sealing element.
Since the clapper armature is arranged directly on the yoke pin, an additional bearing which causes further tolerance considerations is no longer necessary.
Since the clapper armature is in permanent contact with the yoke pin in the region of the bearing thereof, the magnetic contact resistance can further be kept at a low level.
Furthermore, the armature cannot change its position in translation owing to a suitable arrangement, for example, a shell-like arrangement, of the clapper armature on the yoke pin. In addition, the direct magnetic flux between the yoke pins and the armature ensures a very compact unit in constructional terms.
In order to prevent damage to the coil by the fluid, the coil is generally separated from the fluid region, as is also the case, for example, in EP-A-0 872 675. The separation is effected between the coil and the valve housing so that it is necessary to connect the two components with sealing means. However, that has the disadvantage that the tolerances which occur as a result have to be compensated for. The coil is usually separated from the fluid region by seals, the coil and valve housing optionally being in the form of separate components.
In a preferred embodiment of the present invention, the valve housing is formed in one piece and, at the same time, forms the coil element so that the coil is wound directly onto the valve housing.
The clapper armature is accordingly located directly in the fluid region. The yoke pins each have, on both sides, a surrounding projection (pine tree profile) which presses sealingly into the valve housing when the yoke pins are pressed in. The interior is reliably sealed with the clapper armature owing to a suitable press-fit between the yoke pins and the valve housing without any need for separate seals.
Since no separation is provided between the coil and the valve housing in that embodiment, there are also no additional tolerances at that point.
In another embodiment of the invention, the clapper armature projects beyond the second yoke pin with the end thereof that co-operates with the sealing element. Owing to a construction of that type, there is produced at the valve seat a working stroke which is greater than the stroke at the working air gap in the magnetic circuit. The force available is also increased as a result at the valve seat relative to a conventional construction, in particular when the principle of the plunger-type armature is used, wherein the stroke at the working air gap in the magnetic circuit corresponds to the stroke at the valve seat. The larger force with a smaller stroke in the magnetic circuit is produced by the increase in the force curve with decreasing distance, as a result of which the mean force becomes greater relative to the plunger-type armature solution.